U.S. patent application number 14/004787 was filed with the patent office on 2013-12-26 for injection-molding press.
This patent application is currently assigned to LINDAL FRANCE SAS. The applicant listed for this patent is Herve Bodet, Dominique Fournet. Invention is credited to Herve Bodet, Dominique Fournet.
Application Number | 20130341828 14/004787 |
Document ID | / |
Family ID | 45894456 |
Filed Date | 2013-12-26 |
United States Patent
Application |
20130341828 |
Kind Code |
A1 |
Bodet; Herve ; et
al. |
December 26, 2013 |
INJECTION-MOLDING PRESS
Abstract
An injection-molding press for overmolding a second part onto a
first part (8) includes a movable portion and a fixed portion, with
a first mold element (11, 12) on one of the press portions and a
second mold element (20) on the other press portion so as to form a
cavity (C) between the mold portions (11, 12, 20) when the press is
closed. The first mold portion (11, 12) has a first support surface
(125a) movable in the first mold portion and the second mold
portion (20) has a second support surface (22a). In the closed
position of the press with a first part (8) in the first mold
portion and the first support surface (125a) advanced in the
working position, at least a portion (8b) of the front end of the
first part (8) is clamped between the two support surfaces (125a,
22a), forming a tight seal for the cavity (C).
Inventors: |
Bodet; Herve; (Verdun,
FR) ; Fournet; Dominique; (Belleville sur Meuse,
FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bodet; Herve
Fournet; Dominique |
Verdun
Belleville sur Meuse |
|
FR
FR |
|
|
Assignee: |
LINDAL FRANCE SAS
Briey
FR
|
Family ID: |
45894456 |
Appl. No.: |
14/004787 |
Filed: |
March 20, 2012 |
PCT Filed: |
March 20, 2012 |
PCT NO: |
PCT/EP2012/054870 |
371 Date: |
September 12, 2013 |
Current U.S.
Class: |
264/279 ;
425/129.1 |
Current CPC
Class: |
B29C 45/14008 20130101;
B29L 2023/20 20130101; B29C 45/14598 20130101; B29C 33/76 20130101;
B29C 2045/14934 20130101 |
Class at
Publication: |
264/279 ;
425/129.1 |
International
Class: |
B29C 45/14 20060101
B29C045/14 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 4, 2011 |
FR |
1152864 |
Claims
1. Injection-molding press for overmolding by injection-molding a
second part on a first part, comprising: a movable portion and a
fixed portion, at least a first mold element arranged on one of the
portions of the press and at least a second mold element arranged
on the other portion of the press so as to form a cavity between
the two mold portions when the press is closed, the first mold
portion being provided with a first support surface and the second
mold portion being provided with a second support surface, the two
support surfaces being disposed in their respective mold portions
so that, in the closed position of the press with a first part
inserted in the first mold portion, at least a portion of the front
end of the first part is clamped between the first and second
support surfaces so as to form a tight seal for the cavity, wherein
the first support surface is movable in the first mold portion and
the first support surface is movable between a retracted position
and an advanced position, called working position, so that in the
closed position of the press with a first part inserted into the
first mold portion and with the first support surface in the
advanced position, at least a portion of the front end of the first
part is clamped between the first and second support surfaces so as
to form a tight seal for the cavity during the entire duration of
injection.
2. Press according to claim 1, wherein the first mold portion
comprises a core and the second mold portion is constituted by a
matrix.
3. Press according to claim 2, wherein the core is arranged on the
movable portion of the press and the matrix is arranged on the
fixed portion of the press.
4. Press according to claim 2, wherein the core comprises a hollow
cylindrical part and a valve disposed partially inside the
cylindrical part, the valve being movable relative to the
cylindrical part between a retracted position and an advanced
position in which, when the press is closed, the first support
surface is pressed against the second support surface with the
interposition of at least a portion of the front end of the first
part.
5. Press according to claim 4, wherein the first support surface
includes a portion of the top face of the valve, and the second
support surface includes a portion of the bottom wall of the
matrix.
6. Press according to claim 5, wherein the first support surface
and the second support surface have an annular shape surrounding
the cavity.
7. Press according to claim 4, wherein the valve comprises a rod
terminated at its front side by a head having a larger cross
section, said head being provided with a cylindrical wall having
the same external contour as the cylindrical portion of the core
and being closed in the direction of the matrix by a top wall, the
peripheral portion of which constitutes the first support surface
and the center of which constitutes a portion of the molding
surface for the second part and delimits a portion of the
cavity.
8. First mold portion for a press according to claim 1, comprising
a first support surface movable in the first mold portion for
clamping, between itself and a corresponding support surface of a
second mold portion, at least a portion of the front end of a first
part inserted in the first mold portion so as to form a tight seal
for the cavity during the entire duration of injection.
9. First mold portion according claim 8, comprising a core
constituted by a hollow cylindrical part and a valve disposed
partially inside the cylindrical part, the valve being movable
relative to the cylindrical part between a retracted position and
an advanced position in which, when the press is closed in the
direction of the matrix, the first support surface is pressed
against the second support surface with the interposition of at
least a portion of the front end of the first part.
10. First mold portion according to claim 9, wherein the first
support surface is constituted by a portion of the top face of the
valve.
11. First mold portion according to claim 10, wherein the first
support surface has an annular shape.
12. First mold portion according to claim 9, wherein the valve
comprises a rod terminated at its front by a head having a larger
cross section, said head being provided with a cylindrical wall
having the same external contour as the cylindrical part of the
core and being closed in the direction of the matrix by a top wall,
the peripheral portion of which constitutes the first support
surface and the center of which constitutes a portion of the
molding surface for the second part and delimits a portion of the
cavity.
13. Method for overmolding a second part on a first part in an
injection-molding press according to claim 1, wherein the following
steps are performed: a. opening the press; b. positioning a first
part on or in the first mold portion; c. closing the press; d.
injection-molding the second part onto the first part in the cavity
formed between the two mold portions; e. opening the press; f.
ejecting the finished object and returning to step (b), wherein in
step (c) or during a step (c1) following step (c) and prior to step
(d), at least a portion of the front end of the first part is
clamped between the first support surface and the second support
surface so as to form a tight seal for the cavity , and in step (e)
or during a step (d1) following step (d) and prior to step (e), the
clamping of the front end portion of the first part is removed.
14. The method as claimed in claim 13, wherein at least one of the
clamping of step (c) or (c1) and the removal of this clamping in
step (e) or (d1) is obtained by moving the first support surface
relative to the second support surface.
15. The method of claim 13, wherein at least one of the clamping of
step (c) or (c1) and the removal of this clamping in step (e) or
(d1) is obtained by moving the valve relative to the cylindrical
part.
16. The method of claim 14, wherein at least one of the clamping of
step (c) or (c1) and the removal of this clamping in step (e) or
(d1) is obtained by moving the valve relative to the cylindrical
part.
17. Press according to claim 3, wherein the core comprises a hollow
cylindrical part and a valve disposed partially inside the
cylindrical part, the valve being movable relative to the
cylindrical part between a retracted position and an advanced
position in which, when the press is closed, the first support
surface is pressed against the second support surface with the
interposition of at least a portion of the front end of the first
part.
18. Press according to claim 17, wherein the first support surface
includes a portion of the top face of the valve, and the second
support surface includes a portion of the bottom wall of the
matrix.
19. Press according to claim 18, wherein the first support surface
and the second support surface have an annular shape surrounding
the cavity.
20. Press according to claim 17, wherein the valve comprises a rod
terminated at its front side by a head having a larger cross
section, said head being provided with a cylindrical wall having
the same external contour as the cylindrical portion of the core
and being closed in the direction of the matrix by a top wall, the
peripheral portion of which constitutes the first support surface
and the center of which constitutes a portion of the molding
surface for the second part and delimits a portion of the cavity.
Description
[0001] The invention relates to an injection molding press for
overmolding by injection-molding a second part on a first part. The
press includes a movable portion and a fixed portion, at least a
first mold element being positioned on one of the portions of the
press and at least a second mold element being positioned on the
other portion of the press so as to form a cavity between the two
mold portions when the press is closed. The first mold portion is
provided with a first support surface and the second mold portion
is provided with a second support surface, the two support surfaces
being disposed in their respective mold portions so that in the
closed position of the press, with a first part inserted in the
first mold portion, at least a portion of the front end of the
first part is clamped between the two support surfaces so as to
form a tight seal for the cavity. The invention also relates to a
method of using the press of the invention.
[0002] It is increasingly common to mold a second part on a first
part by overmolding. This technique is used, for example, to inject
dispensing heads atop skirts for manufacturing tubes. This requires
the use of a press constituted by a fixed portion and a movable
portion. One or more matrices are arranged on the fixed part, for
example, and a same number of cylindrical cores are placed on the
movable portion facing the matrices. The movable portion is moved
away from the fixed portion, skirts are strung onto the cores, then
the press is closed by moving the movable portion toward the fixed
portion. The front ends of the skirts enter the cavity formed by
the space located between the top face of the core and the bottom
of the matrix. The dispensing head is then injected into the
cavity. The injection pressure is in the order of 500 to 600 bar
per matrix. It is therefore imperative to adjust the cylindrical
surface of the core exactly to the internal diameter of the skirts
and to adjust the cylindrical surface of the front portion of the
matrix, the portion located toward the core, exactly to the
external diameter of the skirts, in order to ensure a perfect seal
for the cavity and thus prevent leakage of the injected mass. This
surface accuracy involves substantial costs.
[0003] Documents FR 2532882 A1, FR 2527510 A1 and JP 5 008260 A all
describe injection presses for overmolding a second part on a first
part by injection molding. The presses have each a mobile portion
and a fixed portion, a first mold element being arranged on one of
the portions of the press and at least a second mold element being
arranged on the other portion of the press so as to form a cavity
between the two mold portions when the press is closed. The first
mold portion is provided with a first support surface and the
second mold portion is provided with a second support surface, the
two support surfaces being disposed in their respective mold
portions so that in the closed position of the press, with a first
part inserted in the first mold portion and with the first support
surface advanced in a working position, at least a portion of the
front end of the first part is clamped between the two support
surfaces so as to form a tight seal for the cavity. In the first
document, the clamping is performed between the top of the
cylindrical portion of the core and the peripheral edge of the
matrix. In the second, which explains well the leakage problem
mentioned above, the proposed solution is an annular flange located
at the top of the core and which comes to clamp the top of the
skirt against a corresponding support surface of the matrix. The
application and removal of clamping are thus associated with the
closing and opening of the press, respectively.
[0004] However, it can be useful to apply the clamping only after
the mold has been closed, or to remove the clamping before opening
the mold. The aim of the invention is therefore to allow clamping
and removing the clamping between the time of closing the mold and
the time of opening.
[0005] This aim is achieved in that the first support surface is
movable in the first mold portion and in that moving means are
provided for moving the first support surface between a retracted
position and an advanced position, called working position, so that
in the closed position of the press, with a first part inserted in
the first mold portion and with the first support surface advanced
in the working position, at least a portion of the front end of the
first part is clamped between the two support surfaces so as to
form a tight seal for the cavity for the entire duration of
injection. Under these conditions, the tight sealing of the cavity
is provided by the clamping of at least a portion of the front end
of the first part between the two support surfaces. If the support
surface is in the retracted position, closing the press does not
cause any clamping of the first part. It is first necessary to move
the first support surface to its working position to cause the
clamping. Likewise, it is possible to remove the clamping after
injection, but before opening the press. Since the first part is
made of a plastic material, it is sufficiently deformed under the
pressure exerted by the two support surfaces to provide a tight
seal at their interface without requiring a particularly high
accuracy for the support surfaces, nor, for that matter, for the
rest of the mold portions.
[0006] In a preferred exemplary embodiment of the invention, the
first mold portion is constituted by a core and the second mold
portion is constituted by a matrix, the core being preferably
arranged on the movable portion of the press and the matrix being
preferably arranged on the fixed portion of the press.
[0007] When the first part is cylindrical, preferably, the core is
constituted by a hollow cylindrical part and a valve disposed
partially inside the cylindrical part, means being provided for
moving the valve relative to the cylindrical part between a
retracted position and an advanced position in which, when the
press is closed, the first support surface is pressed against the
second support surface with interposition of at least a portion of
the front end of the first part. In this case, the first support
surface can be constituted by a portion of the top face of the
valve, and the second support surface by a portion of the bottom
wall of the matrix. The first support surface and the second
support surface have an annular shape surrounding the cavity.
[0008] Preferably, the valve is constituted by a rod ending at its
front side with a head having a larger cross section, said head
being provided with a cylindrical wall having the same external
contour as the cylindrical part of the core, and being closed in
the direction of the matrix by a top wall, the peripheral portion
of which constitutes the first support surface and the center of
which constitutes a portion of the molding surface for the second
part and delimits a portion of the cavity.
[0009] The invention also relates to a method for using the press.
This method comprises the following steps:
[0010] (a) opening the press;
[0011] (b) positioning a first part on or in the first mold
portion;
[0012] (c) closing the press;
[0013] (d) injection molding the second part on the first part in
the cavity formed between the two mold portions;
[0014] (e) opening the press;
[0015] (f) ejecting the finished object and returning to step
(b).
[0016] The method of the invention is characterized in that, in
step (c) or during a step (c1) prior to step (d) and following step
(c), at least a portion of the front end of the first part is
clamped between the first support surface and the second support
surface so as to form a tight seal for the cavity.
[0017] Likewise, the clamping of the front end portion of the first
part can be removed in step (e) or during a step (d1) following
step (d) and prior to step (e).
[0018] The clamping in step (c) or (c1) and/or the removal of this
clamping in step (e) or (d1) can be obtained by moving the first
support surface relative to the second support surface so as to
move them toward each other or away from each other. This clamping
can be obtained in particular by moving the valve member relative
to the cylindrical part.
[0019] The invention is described in more detail below using the
figures which show:
[0020] FIG. 1: a cross sectional view of the core and the matrix,
the press being closed and the valve being in the retracted
position;
[0021] FIG. 2: a cross sectional view similar to FIG. 1, but in
which the valve is in an advanced position;
[0022] FIG. 3: a view of the enlargement portion B of FIG. 1, the
valve being in a retracted position;
[0023] FIG. 4: a view of the enlargement portion D of FIG. 2, the
valve being in the forward position;
[0024] FIG. 5: a schematic view of the position of the matrix and
the core when the press is open;
[0025] FIG. 6: a cross sectional isometric view of the valve
head;
[0026] FIG. 7: a cross sectional isometric view of the matrix;
[0027] FIG. 8: an enlarged view of the clamping zone when the valve
is in the advanced position; and
[0028] FIG. 9: a view of an example of a tube obtained with the
press and the method of the invention.
[0029] The device of the invention is intended to simplify a press
for overmolding a second part on a first part. In the present
example, a dispensing head (9), constituting the second part, is to
be overmolded on a skirt (8), forming the first part, so as to form
a tube formed as a single piece.
[0030] By convention, it is decided that the front portion of the
core (10), of the cylinder (11), of the valve (12) or of the skirt
(8) is the portion of the respective element that is located on the
side of the matrix (20), that is to say, to the right on the
figures. By analogy, the front portion of the matrix (20)
corresponds to the portion of the matrix located on the side of the
core (10).
[0031] Overmolding presses include a fixed portion and a movable
portion each carrying a table; these elements are not shown. In
general, the matrix (20) of the part to be overmolded is located on
the fixed part, while the core (10) is located in the movable part.
The matrix (20) constitutes the second mold element while the core
(10) constitutes the first mold element.
[0032] The movable portion is first moved away from the fixed
portion, as shown schematically in FIG. 5, and the first part,
here, the skirt (8), is placed on the core (10). The press is then
closed so that the core extends partially into the matrix, as well
as the front end (8a, 8b, 8c) of the skirt (8).
[0033] According to the invention, the core (10) is constituted by,
not only a cylindrical wall onto which the skirt (8) is slid, but
also a valve (12). To this effect, the cylindrical wall is
constituted by a hollow cylinder (11) within which the valve (12)
can be moved by moving means which are not shown. These means can
be constituted by hydraulic or pneumatic pistons or by cams, for
example.
[0034] This valve (12) is essentially constituted by a rod (121)
and by a head (122) which is wider than the rod. The rear face
(123) of this head is partly frusto-conical, the taper widening
toward the top face. This frustoconical wall is extended by a
cylindrical wall (124) and a top wall (125). The contour of the
cylindrical wall (124) corresponds to the contour of the outer face
of the cylinder (11) and to the inner contour of the skirt. In
general, the contour is a circle. However, it is possible to
provide an ellipsoidal contour or any other suitable shape. In
other words, the cylindrical wall (124) and the outer face of the
cylinder have the same transverse cross section. The top wall (125)
is divided into two portions: its circumferential edge (125a),
which serves as a support surface, and its center (125b), which
serves as a molding surface for the inner side of the second part,
here, the dispensing head (9).
[0035] The front edge (112) of the cylinder (11), oriented toward
the matrix (20), is also tapered, the taper widening towards the
front, that is to say, in the direction of the matrix (20). This
frustoconical surface (112) has a shape complementary to the
frustoconical shape of the rear face (123) of the valve head. It
serves as a backstop for the latter (123) when the valve is in the
retracted position. The term (tron)conical means, not only the cone
of revolution, but also other types of cone defined by the
periphery of the skirt.
[0036] The outer periphery of the cylinder (11) and of the
cylindrical wall (124) of the valve (12) corresponds substantially
to the inner periphery of the skirts (8). In general, they are
circles or ellipses.
[0037] The matrix (20) comprises a recess having a cylindrical wall
(21) which is extended by a bottom wall (22). This bottom wall (22)
has two functions: its circumferential edge (22a) serves as a
support surface, while its center (22b) serves as a molding surface
for the outer face of the second part, here, the dispensing head
(9).
[0038] The inner periphery of the cylindrical wall (21) of the
matrix corresponds substantially to the outer periphery of the
skirts (8). The support surface (22a) of the matrix (20) has a
shape complementary to the support surface (125a) of the valve.
[0039] In order to operate, the support surfaces (125a, 22a) must
not be parallel to the displacement movement of the movable portion
of the press and/or to that of the valve (12), otherwise, there
would no clamping effect. In the examples presented here, the
support surfaces are inclined towards the center relative to the
direction of movement of the press and/or of the valve so that the
front end (8a, 8b, 8c) of the skirt (8) tends to close. As seen in
the example of tube shown on FIG. 9 obtained by the method, the
inclination of the support surfaces does not need to be very
important, and in particular, it does not need to be as important
as that shown on FIGS. 1 to 5 and 8, which have only a schematic
value.
[0040] The press of the invention operates as follows:
[0041] (a) The press is opened and the valve is retracted, if this
was not already done.
[0042] (b) The first part, here, the skirt (8), is then placed on
the cylinder (11). Means not shown limit the entry movement of the
skirt beyond the desired position. These means can be, for example,
length-setting rings as a function of the skirts used. The front
end of the skirt protrudes slightly beyond the cylindrical wall
(124) of the valve in the direction of the matrix.
[0043] (c) The press is then closed. The end (8a, 8b, 8c) of the
skirt which extends beyond the cylinder (11) projects into the
cylindrical portion (21) of the matrix, then deforms slightly
following the shape inclined towards the center of the bottom wall
(22). Meanwhile, the front end of the core, essentially the valve
head (122), also projects into the recess of the matrix. When the
press is closed, the position shown in FIGS. 1 to 3 is obtained. In
this position, there is no sealing between the matrix and the
core.
[0044] (c1) The valve (12) is now moved into the advanced position
shown in FIGS. 2, 4 and 8. In this position, a portion (8b) of the
front end of the skirt is thus clamped between the support surface
(125a) of the valve and the support surface (22a) of the matrix.
The pressure exerted by the support surface (125a) of the valve on
the matrix (20) and on the portion (8b) of the skirt clamped
between the two support surfaces (125a, 22a) is at least equal to
the injection pressure, that is to say, in the order of 500 to 600
bar. The clamping zone (P) is marked in FIGS. 8 and 9. Since these
two surfaces are annular, a seal is formed so as to tightly seal
the cavity (C) in which the second part will be molded. This cavity
(C) is formed by the space located between the center (125b) of the
top wall of the valve and the center (22b) of the bottom wall of
the matrix.
[0045] (d) The second part, here, the dispensing head (9), is
injected into the cavity (C). During injection, the mass cannot
escape from this cavity.
[0046] (d1) The valve (12) is retracted.
[0047] (e) The press is opened.
[0048] (f) The finished tube is ejected. The process can start over
at step (b).
[0049] The retraction of the valve (12), instead of being performed
in step (dl), can be performed between step (e) and step (f), in a
step (el). Thus, it is the opening of the press in step (e) that
causes the clamping to be removed. The support surface (125a) is
placed in the working position (clamping the portion of the front
end of the first part 22a between it and the second support surface
22a) before the start of the injection, remains in this position
throughout the injection, and is retracted only after the injection
is completed. The tight seal formed by clamping the portion of the
front end of the first part between the two support surfaces
persists during the entire duration of injection.
[0050] If the core is not provided with a valve, the steps (c1) and
(d1) and (e1) are not performed. The support surfaces are moved
toward each other or away from each other solely by the closing or
opening of the press in steps (c) and (e).
[0051] To increase the fusion interface between the first part,
here, the skirt (8), and the second part, here, the dispensing head
(9), it is possible to provide a portion (8c) of the skirt beyond
the portion (8b) clamped between the two support surfaces, this
front end (8c) thus projecting into the overmolding cavity. This
way, overmolding does not occur only in the area of the front edge
of the skirt, as is the case in FIG. 4, but also on the inner
surface of the portion (8c) of the skirt that projects from the
clamping zone between the support surfaces into the overmolding
cavity. This is the case with the embodiment of FIG. 8.
[0052] To ensure sealing of the press, it is thus sufficient that
the annular portion forming the support surface (125a) of the valve
head is substantially adjusted to the geometry of the support
surface (22a) of the matrix. Since a portion (8b) of the front end
of the skirt is interposed between these two surfaces, accuracy
does not need to be very high.
[0053] Neither the surface accuracy of the cylinder (11), nor the
surface accuracy of the cylindrical portion (124) of the valve head
and that of the cylindrical portion (21) of the matrix, play any
role in the sealing. The cost for manufacturing these parts is thus
greatly reduced.
[0054] This method is not limited to the overmolding of a circular
part on the front face of a cylindrical part. The method is very
easily adaptable to the overmolding of a dispensing head (9)
closing the top of the cylinder constituting the skirt (8) and
provided with a hinged cap (9a) positioned eccentrically relative
to the skirt, like the tube shown on FIG. 9.
[0055] More generally, the method can be applied to any first part,
even a non-cylindrical part, having a front end that can be wedged
between two support surfaces, one belonging to the movable portion
and the other to the fixed portion of the press, so that the
portion clamped between the two support surfaces forms a tight seal
for the overmolding cavity. Due to the clamping between the two
support surfaces to which this front end is subjected, it is
deformed on its sides so as to ensure the lateral sealing between
the two support surfaces. To this effect, the movement of the valve
does not need to take place parallel to the direction of movement
of the movable portion of the press.
[0056] The method is intended for overmolding by injection-molding
a plastic material on another plastic material. In general, the two
materials are compatible, that is to say, they merge together
during molding. However, it is also possible to provide
incompatible materials if the geometry of the two parts is such
that anchoring means are formed. In particular, it is possible to
provide anchoring means on the portion (8c) of the skirt that
projects into the cavity beyond the clamping zone (8b, p).
[0057] The movable valve (12) makes it possible to compensate for
variations in the thicknesses of the skirts due to extrusion
tolerances as well as in the heights of the skirts due to length
cutting tolerances.
LIST OF REFERENCES
[0058] 8 First part (skirt) [0059] 8a Portion of the skirt which
projects into the matrix, without reaching the clamping zone [0060]
8b Portion of the skirt located in the clamping zone [0061] 8c
Portion of the skirt located beyond the clamping zone [0062] 9
Second part, i.e., part to be overmolded (dispensing head) [0063]
10 Core (first mold portion) [0064] 11 Cylinder [0065] 12 Valve
[0066] 121 Rod of the valve [0067] 122 Head of the valve [0068] 123
Conical rear wall of the head [0069] 124 Cylindrical wall of the
head [0070] 125 Top wall of the head [0071] 125a Support surface of
the top wall [0072] 125b Molding surface [0073] 20 Matrix (second
mold portion) [0074] 21 Cylindrical wall [0075] 22 Bottom wall
[0076] 22a Support surface [0077] 22b Molding surface [0078] P
Clamping zone [0079] C Cavity for injection of the second part
* * * * *